简单的 JavaScript 数学没有意义

Question

I feel like I'm a novice again. I thought I was long past these problems. below is a simple script with two function neither of which work. What am I missing. Any help appreciated.

 function calculator() { var bee = document.getElementById("beerPerc").value; var win = document.getElementById("winePerc").value; var liq = 100 - (bee + win); document.getElementById("liquorPerc").value = liq; } function calculator2() { document.getElementById("liquorPerc").value = parseInt(100 - (document.getElementById("beerPerc").value + document.getElementById("winePerc").value)) }

 <div id="calcArea"> <div> <input type="number" id="beerPerc" value="50" onkeyup="calculator2()"> &nbsp; % of Beer Drinkers<br> <input type="number" id="winePerc" value="30" onkeyup="calculator2()"> &nbsp; % of Wine Drinkers<br> <input type="number" id="liquorPerc" onkeyup="calculator2()"> &nbsp; % of Liquor Drinkers<br> </div> </div>

Answer 1

Two things:

1. Case is significant. If you declare the variable bee , you can't read it with Bee .

2. .value is always a string. You need to convert the strings to numbers:

    var bee = Number(document.getElementById("beerPerc").value);

If you don't do this, + will perform string concatenation, not addition.

You don't need to call parseInt() on the result of a numeric calculation, that's always a number.

function calculator2() {
    document.getElementById("liquorPerc").value = 100 - (parseInt(document.getElementById("beerPerc").value, 10) + parseInt(document.getElementById("winePerc").value, 10)))
}